The present invention relates to an image sensing apparatus for forming a frame image by using a single solid-state image sensor.
A popular apparatus currently used for reproducing an image signal is a television receiver. One of the signals to be inputted to the television receiver is a video signal conforming with the PAL or NTSC system which adopts an interlaced scanning system.
Therefore, if a television receiver receiving such a video signal is to be used, it is necessary to provide an image sensing apparatus, which generates video signals processed by interlaced scanning, i.e., odd and even field signals. To this end, a frame image sensor is mostly used in image sensing apparatus, except those simple apparatus for field image sensing.
As a frame image sensor, there is known a sensor of the type that image sensing cells for odd and even fields are alternatively arranged. However, a sufficient number of image sensing cells of the frame image sensor cannot be realized in the horizontal direction due to certain problems of current LSI technology. Therefore, to obtain a high resolution of an image, it is necessary to utilize vertical correlation of the image. Furthermore, it is necessary to make the frame image sensor compatible with both stationary and dynamic image sensing.
In view of the above problem associated with the frame image sensor, vertical correlation and so on, it is hard to say that a fine quality of image can be obtained with present image sensors which read an image through transfer of electrical charges which have been accumulated upon light excitation.
For instance, in the case of an image sensor alternatively disposing odd and even field image sensing cells, such as conventional IL-CCD, X-Y address type MOS and the like, it is necessary to provide such expedients as delay lines for performing a vertical correlation process. Therefore, a complicated circuit arrangement is required, and moreover there arises a problem that a false signal is liable to occur due to a long distance in vertical correlation.
A solid-state image sensor solving the above problem of correlation distance is disclosed as an X-Y address type MOS in the Japanese Unexamined Publication (Kokai) No. 50684/1984. However, in this case, an additional signal processing system and a stationary image recording head capable of writing both odd and even fields at the same time are required. Therefore, some problems arise in its circuit and cost.